CAN PRETREATMENT FOR IMPROVED COATING ADHESION

摘要

The invention relates to the use of an acidic aqueous composition for pretreating cans, wherein an inorganic-organic conversion layer is formed in the course of the pretreatment, said conversion layer, as such, offering an excellent adhesive base for wax which improves sliding of the formed can and for the subsequent coating. The invention relates to a wet-chemical pretreatment method in which a can cylinder is first contacted with an acidic aqueous composition that contains water-soluble inorganic compounds of Zr, Ti, Si, Hf or Ce, and water-soluble polymers comprising carboxyl groups or hydroxyl groups; and subsequently is contacted with an aqueous wax dispersion. The invention further relates to an acidic aqueous composition suitable for the pretreatment method comprising water-soluble polymers selected from condensation products of glycoluril and aldehydes. The invention further relates to a method for producing can cylinders, said method including the pretreatment according to the invention.

主权项

1. A process for surface-treating a can cylinder which is deep-drawn from a metal sheet and is open at one end, comprising steps of:
(i) contacting at least an outer circumferential surface of a can cylinder that is open at one end with an acidic aqueous composition containing:
a) at least one water-soluble inorganic compound of an element selected from Zr, Ti, Si, Hf, Ce and combinations thereof; andb) at least one water-soluble organic resin, which comprises at least carboxyl groups or hydroxyl groups, having an acid value and/ or a hydroxyl value wherein a sum of the acid value and/or hydroxyl value of the at least one water-soluble organic resin is at least 50 mg KOH/g; and subsequently—with or without an intermediate flushing step— (ii) contacting at least the outer circumferential surface of the can cylinder from step (i) with an aqueous dispersion of a wax.